Roll fuser

ABSTRACT

A contact fuser assembly for use in an electrostatic reproducing apparatus including an internally heated metal core cooperating with a resilient backup roll to form a nip through which substrates carrying toner images are moved with the toner images contacting the metal core. The fuser assembly is characterized by the provision of cleaning mechanism which collects nonvisual toner from the metal core as well as removing excess release agent material therefrom, the release agent material being applied to the surface of the core in order to enhance release of contaminates. The cleaning mechanism is characterized by the provision of thermally conductive members contacting the core, which members are cooled by positive cooling means.

[ 1 Dec. 30, 1975 1 1 ROLL FUSER [75] Inventor: Raghulinga R. Thettu, Webster,

[73] Assignee: Xerox Corporation, Stamford,

Conn.

[22] Filed: Jan. 2, 1975 [21] Appl. No.: 537,883

5/1974 Ariyama et al. 118/60 6/1974 Thetty et al. 432/228 Primary Examiner-Mervin Stein Assistant ExaminerDouglas Salser [57] ABSTRACT A contact fuser assembly for use in an electrostatic reproducing apparatus including an internally heated metal core cooperating with a resilient backup roll to form a nip through which substrates carrying toner images are moved with the toner images contacting the metal core. The fuser assembly is characterized by the provision of cleaning mechanism which collects nonvisual toner from the metal core as well as removing excess release agent material therefrom, the release agent material being applied to the surface of the core in order to enhance release of contaminates. The cleaning mechanism is characterized by the provision of thermally conductive members contacting the core, which members are cooled by positive cooling means.

16 .Claims, 2 Drawing Figures US. Patent Dec. 30, 1975 3,929,095

ROLL FUSER BACKGROUND OF THE INVENTION of plain paper with subsequent affixing of the image thereto.

In order to permanently affix or fuse electroscopic toner material onto a support member by heat, it is necessary to elevate the temperature of the toner material to a point at which the constituents of the toner material coalesce and become tacky. This action causes the toner to be absorbed to some extent into the fibers of the support member which, in many instances, constitutes plain paper. Thereafter, as the toner material cools, solidification of the toner material occurs causing the toner material to be firmly bonded to the support member. In both the xerographic as well as the electrographic recording arts, the use of thermal en'- ergy for fixing toner images onto a support member is old and well known.

One approach to thermal fusing of electroscopic toner images onto a support has been to pass the support with the toner images thereon between a pair of opposed roller members, at least one of which is internally heated. During operation ofa fusing system of this type, the support member to which the toner images are electrostatically adhered is moved through the nip formed between the rolls with the toner image contacting the heated roll to thereby effect heating of the toner images within the'nip. By controlling the heat transferred to the toner, virtually no offset of the toner particles from the copy sheet to the fuser roll is experienced under normal conditions. This is because the heat applied to the surface of the roller is insufficient to raise the temperature of the surface'of the roller above the hot offset temperature of the toner whereat the toner particles in the image areas of the toner would liquify and cause a splitting action in the molten toner to thereby result in hot offset. Splitting occurs when the cohesive forces holding the viscous toner mass together areless than the adhesive forces tending to offset it to a contacting surface such as a fuser roll.

However, toner particles will be offset to the fuser roll by an insufficient application of heat to the surface thereof (i.e. cold offsetting); by imperfections in the properties of the surface of the roll; or by the toner particles insufficiently adhering to the copy sheet by the electrostatic forces which normally hold them there. In such a case, toner particles may be transferred to the surface of the fuser roll with subsequent transfer to the backup roll during periods of time when no copy paper is in the nip.

Moreover, toner particles can be picked up by the fuser and/or backup roll during fusing of duplex copies or simply from the surroundings of the reproducing apparatus.

One arrangement for minimizing the problems attendant the foregoing, particularly that which is commonly referred to as offsetting has been to provide a fuser roll with an outer surface or covering of polytetrafluoroethylene, commonly known as Teflon, to which a release agent such as silicone oil is applied, the thickness of the Teflon being on the order of several mils and the thickness of the oil being less than 1 micron. Silicone based oils, which possess a relatively low surface energy, have been found to be materials that are suitable for use in the heated fuser roll environment where Teflon constitutes the outer surface of the fuser roll. In practice, a thin layer of silicone oil is applied to the surface of the heated roll to thereby form an interface between the roll surface and the toner images carried on the support material. Thus a low surface energy layer is presented to the toner as it passes through the fuser nip and thereby prevents toner from offsetting to the fuser roll surface. The foregoing notwithstanding, non-visual offset (i.e. offsetting of very fine particles of toner) does occur. In prior art constructions (fuser structures where the outer surface comprises Teflon or silicone rubber) such offsetting has been combated by the employment of various cleaning members, the wick material employed for applying the silicone based oil to the fuser roll serving this purpose.

However, it has been found that cleaning systems which are known to work with the aforementioned types of fuser roll surfaces are not acceptable for utilization with metal roll fusers.

Accordingly, the primary object of this invention is to provide a new and improved contact fuser system for fixing toner images to substrates.

A more particular object of this invention is to provide a fuser roll cleaning structure for utilization with a metal'roll fuser.

Another object of this invention is to provide a contact fuser system employing a metal fuser roll structure and a cleaning mechanism therefor, such mechanism comprising thermally conductive portions contacting the metal fuser roll and being characterized by the provision of cooling means therefor.

BRIEF SUMMARY OF THE INVENTION Briefly, the above-cited objects are accomplished by the provision of a contact fuser apparatus comprising a metal fuser roll structure cooperating with a resilient backup roll to form a nip through which substrates carrying toner images are passed with the toner images contacting the fuser roll structure.

A cleaning structure having portions thereof contacting the metal roll serves to remove non-visual toner and other contaminates therefrom. The cleaning structure, in one embodiment of the invention, is characterized by a plurality of metal fingers contacting the roll surface and a positive cooling device reduces the temperature of the fingers to thereby enhance the toner removal.

In a second embodiment of the invention the fingers are replaced by a pair of heat conductive rolls.

Other objects and advantages of the present invention will become apparent when read in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of a contact fuser representing the invention; and

FIG. 2 is a side elevational view ofa modified form of the fuser illustrated in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Since the xerographic reproducing process is well known, a detailed description thereof is omitted. For those who would consider a description of the xerographic process necessary for a complete understanding of the present invention reference may be had to U.S. Pat. Nos. 3,718,116 and 3,745,972.

As shown in FIG. 1, the present invention comprises a fuser assembly 15 including a heated roll structure 30 including a hollow cylinder or core 31 having a suitable heating element 32 disposed in the hollow portion thereof which is coextensive with the cylinder. The heating element 32 may comprise any suitable type heater for elevating the surface temperature of the cylinder to operational temperatures, therefore, 250400F. For example, it may be a quartz lamp. The cylinder or core 31 is fabricated from any suitable material capable of accomplishing the objects of the present invention. Typical materials are copper, anodized aluminum and alloys thereof, steel, stainless steel, nickel and alloys thereof, nickel plated copper and chrome plated copper. The resulting structure has an outside diameter on the order of 1.5 to 3.0 inches and has a length on the order of to inches. Power requirements for the foregoing are 500-2500 watts peak power with an average power of 300-2000 watts and 75-250 watts for standby.

The surface temperature of the fuser roll structure is controlled by contacting the surface thereof with a thermistor probe 45 in a manner described in U.S. Pat. No. 3,327,096, issued in 1967 to Bernous and incorporated herein by reference.

The fuser assembly 15 further comprises a backup roll structure 33 which cooperates with the fuser roll structure 30 to form a nip 34 through which a copy paper or substrate 35 passes such that toner images 36 thereon contact the fuser roll structure. The backup roll structure may comprise any suitable construction, for example, a steel cylinder, but preferably comprise a rigid steel core 37 having a Viton elastomer surface or layer 38 thereon. A suitable roll has a core approximately 1.8 inches in diameter with a 0.1 inch cover or layer structure of Viton elastomer or other suitable high temperature elastomeric layer structure, for example, silicone rubber and a combination of Viton or silicone rubber with Teflon thereon. Viton is a trade mark of the E. l. duPont de Nemours and Co. The specific dimensions of the members making up the backup roll will be dictated by the requirements of the particular copying apparatus wherein the fuser assembly 15 is employed, the dimensions being greater or less depending upon the process speed of the machine. The heated roll and backup roll structures may be mounted on fixed axes, therefore not requiring movement in and out of engagement or they may be mounted in accordance with prior art devices wherein the backup roll is moved into and out of engagement with the fuser roll structure.

Means (not shown) for applying a loading force in a conventional manner to the fuser assembly 15 serves to create nip pressures on the order of 15 to 150 psi average. The durometer of the backup roll is chosen such that dwell times" of 5 to 100 milliseconds can be obtained with loading forces within the aforementioned range of pressures. Dwell time is proportional to the ratio of the nip length to the surface speed of the rolls. For a given angular velocity the surface speeds will vary depending upon the diameter of the rolls. For example, with a 2 inch fuser roll, speeds of 0 to 30 inches per second are attainable and for a 3 inch fuser roll, speeds of 0 to 45 inches per second have been attained. Accordingly, it can be seen that the aforementioned dwell times can be obtained by varying one or the other or both of the dwell time relationships. Durometers of 2090 Shore A have been found to provide satisfactory results.

The aforementioned materials from which the fuser roll structure 30 may be fabricated are relatively high surface energy materials, consequently, hot toner material contacting such surfaces would readily wet the surface of the fuser roll. Accordingly, there is provided a sump 39 for containing release material 40 capable of interacting with the fuser roll. The release material is preferably a low molecular weight material which is solid at room temperature and which has a relatively low viscosity at the operating temperatures of the fuser roll structure. An example of such a material is polyethylene hopolymer manufactured by Allied Chemical Co. and having the designation AC-8 hopolymer.

A metering blade 41 preferably of silicone rubber is mounted to the sump 39 by conventional means such that an edge 42 thereof contacts the fuser roll structure serving to meter the release agent 40 in its liquid state onto the fuser roll. In the preferred embodiment, a blade 0.060 inch thick and having a width of 1.0 inch and length of 15 inches has been employed. By means of such a construction a 0.1-0.5 micron thickness of release agent is applied to the surface of the fuser roll.

A pair of end seals 47, preferably of sponge rubber are provided to contain a release agent material in the sump 39. One or more stripper fingers 50 are provided for insuring removal of the substrate from the fuser roll.

Although the interaction of the polyethylene material with the surface of the fuser roll structure is not well understood, it is believed that a thermal degradation of the polyethylene takes place to form a by-product of carboxylic acid which chemically reacts with the surface of the fuser roll structure. It has been noted that where the polyethylene and the fuser roll surface form a boundary layer with the ambient air, beading of the surface of the fuser roll structure takes place along such boundary. Accordingly, a wiper blade 60 is supported adjacent to the sump 39 in any suitable manner such that it contacts the core 31 to form a wiper blade/- polyethylene/air boundary 62 and thereby prevent the formation of a core/polyethylene/air boundary which would result in the aforementioned formation of a bead on the core which would print out on the copy sheets 14 and also disrupt proper operation of the combination seal and metering blade 41. The wiper blade 60 is preferably fabricated from a material which is compatible with the polyethylene (i.e. does not chemically react therewith and to a lesser degree is dimensionally stable in the presence thereof). To this end, the wiper blade comprises an elastomeric material, for example, silicone rubber.

In accordance with the objects of the present invention, a pair of cleaning roll structures 64 are positioned to clean the fuser roll structure 30 of paper contamination and non-visual offset as well as visual toner offset particles. Each of the cleaning roll structure preferably comprises a metal core member 66 which is covered by a cylindrical sleeve member 68 made of polyester polymer material. Any suitable polyester polymer material having a melting or softening point ranging from about 120 to about 275C can be employed. Typical materials are aliphatic, aromatic or mixtures of aliphatic, aromatic polyesters. Examples of these classes of materials are polyethylene oxolate, ploy-pp xylelene terephthalate, polyethylene/neopentyl terephthalate. Preferred materials of the mixed class of polyesters are PE-IOO or PE-200, trademarks of Goodyear Company, of Akron, Ohio. The sleeve member 68 has a thickness of about 0.005 to about 0.030 inches. The sleeve member may be applied to the metal core member 66 by any suitable technique such as solvent spraying, extrusion wrapping, hot melt rolling or combinations thereof. Preferably the final application is by heat shrinking the extruded polyester tube over the core member. Desirably, hot rolling is applied during the heat shrinking process. While the preferred cleaning roll structure has been set forth hereinabove, it is not desired to limit it to such a construction. The cleaning roll may also comprise an elastomeric roll construction which is covered with toner or it may simply comprise a bare metal roll.

It has been found that paper contamination on the fuser roll structure 30 is physically attracted to the sleeve 68 due to good adhesion at high temperature. The viscosity of the polyester material is such that it has high elongation at the operating temperatures coupled with excellent wetting properties.

Any loose paper fiber and/or background toner particles attracted by the fuser roll surface collect thereon and transfer to the sleeve member 68 by virtue of the physical adhesion of the contamination to the polyester polymer material.

A source of cooling air such as a blower 70 serves to provide air flow across the surface of the cleaning roll structures in order to reduce the temperature in the area of the cleaning to approximately 125175F compared to nip temparatures on the order of 320F. it has been found that the provision of the cooling results in a satisfactory structure for removing contaminates from a metal fuser roll structure.

In the modified form of the invention illustrated in FIG. 2, the cleaning rolls 64 are replaced by a cleaning structure 72 comprising a body portion 74 having a plurality of heat pipes 76 contained therein. Heat pipes of the type designated CA Series by The Heat Pipe Corporation of America, Watchung, NJ. have been found to be satisfactory. A plurality of wiper fingers 78 form an integral structure with the body portion 74. The fingers are thermally conductive and during operation of the fuser they contact the fuser roll structure with a wiping action and are cooled by the heat pipes 76. Recesses 80 intermediate the fingers 78 provide areas for accumulation of contaminates removed from the fuser roll. In lieu of the heat pipes or in combination therewith there may be provided a blower such as 70.

While the invention has been shown and described in conjunction with the preferred embodiment thereof, it will be understood that various modifications thereto may be made by those skilled in the art without the departing from the spirit of the invention and such modifications are intended to be covered by the claims appended hereto. For example, the rolls 64 and blower 6 could be replaced by rolls which contain heat pipes for cooling of the roll surface.

What is claimed is:

l. Fuser apparatus for fixing toner images to substrates through the utilization of heat and pressure, said apparatus comprising:

a metal fuser roll member;

a resilient member cooperating with said metal fuser member to form a nip through which said substrates pass to thereby soften said toner images;

means for applying release agent material to the surface of said metal fuser member to facilitate removal of toner particles and other contaminates therefrom;

cleaning means disposed adjacent said metal fuser member intermediate said nip and said release agent applying means and contacting said fuser member; and

means for removing heat from said cleaning means to maintain the temperature thereof at a level which facilitates removal of toner particles from said fuser member.

2. Apparatus according to claim 1, wherein said cleaning means comprise a plurality of spaced apart heat conductive wiper blades.

3. Apparatus according to claim 2, wherein said metal fuser member comprises an internal source of thermal energy and said toner images contact said metal fuser member.

4. Apparatus according to claim 3, wherein said release material comprises polyethylene.

5. Apparatus according to claim 4, including means for preventing bead formation on said fuser member.

6. Apparatusaccording to claim 5, wherein said cleaning means comprises roll structures.

7. Apparatus according to claim 1, wherein said cleaning means comprises at least one structure supported for rolling contact with said metal fuser member.

8. Apparatus according to claim 7, wherein said metal fuser member comprises an internal source of thermal energy and said toner images contact said metal fuser member.

9. Apparatus according to claim 8, wherein said release material comprises polyethylene.

l0. Apparatus-according to claim 9, including means for preventing'bead formation on said fuser member.

11. Apparatus according to claim 10, wherein said members comprise roll structures.

12. Apparatusaccording to claim 1, wherein said cleaning means comprises a pair of elastomcr cleaning rolls.

13. Apparatus according to claim 1, wherein said cleaning means comprises a pair of metal roll structures.

14. Apparatus according to claim 12, wherein said cleaning rolls contain a polymer coating on the surface thereof.

15. Apparatus according to claim 13, wherein said roll structures contain a polymer coating on the surface thereof.

16. Apparatus according to claim 6, wherein said heat removing means heat pipe means fusing a part of said roll structures. 

1. Fuser apparatus for fixing toner images to substrates through the utilization of heat and pressure, said apparatus comprising: a metal fuser roll member; a resilient member cooperating with said metal fuser member to form a nip through which said substrates pass to thereby soften said toner images; means for applying release agent material to the surface of said metal fuser member to facilitate removal of toner particles and other contaminates therefrom; cleaning means disposed adjacent said metal fuser member intermediate said nip and said release agent applying means and contacting said fuser member; and means for removing heat from said cleaning means to maintain the temperature thereof at a level which facilitates removal of toner particles from said fuser member.
 2. Apparatus according to claim 1, wherein said cleaning means comprise a plurality of spaced apart heat conductive wiper blades.
 3. Apparatus according to claim 2, wherein said metal fuser member comprises an internal source of thermal energy and said toner images contact said metal fuser member. Pg,13
 4. Apparatus according to claim 3, wherein said release material comprises polyethylene.
 5. Apparatus according to claim 4, including means for preventing bead formation on said fuser member.
 6. Apparatus according to claim 5, wherein said cleaning means comprises roll structures.
 7. Apparatus according to claim 1, wherein said cleaning means comprises at least one structure supported for rolling contact with said metal fuser member.
 8. Apparatus according to claim 7, wherein said metal fuser member comprises an internal source of thermal energy and said toner images contact said metal fuser member.
 9. Apparatus according to claim 8, wherein said release material comprises polyethylene.
 10. Apparatus according to claim 9, including means for preventing bead formation on said fuser member.
 11. Apparatus according to claim 10, wherein said members comprise roll structures.
 12. Apparatus according to claim 1, wherein said cleaning means comprises a pair of elastomer cleaning rolls.
 13. Apparatus according to claim 1, wherein said cleaning means comprises a pair of metal roll structures.
 14. Apparatus according to claim 12, wherein said cleaning rolls contain a polymer coating on the surface thereof.
 15. Apparatus according to claim 13, wherein said roll structures contain a polymer coating on the surface thereof.
 16. Apparatus according to claim 6, wherein said heat removing means heat pipe means fusing a part of said roll structures. 